The larger size maternity bras are harder to come by, but you can get them. The very best place is Mothers' Direct (the ABA store). They have a great range of maternity bras even in the bigger sizes. I love their range as they have really attractive ones unlike the usual boring bunch. If you are in Melb, Syd or Bris, you can go in store to be fitted. Otherwise you can order online if you know your size.

Otherwise the department stores such as DJs and Myer have an ok range, and a very small range (if at all) in the larger sizes. Some of the brands have outlet stores with a better range. If you are having trouble you could try ringing the manufacturers to find out where they send their larger size stock to. Or you could always go and be fitted at Myer and order from Mothers Direct (shh, did I say that?).